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| Titel |
Technical note: Water vapour concentration and flux measurements with PTR-MS |
| VerfasserIn |
C. Ammann, A. Brunner, C. Spirig, A. Neftel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 12 ; Nr. 6, no. 12 (2006-10-17), S.4643-4651 |
| Datensatznummer |
250004143
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| Publikation (Nr.) |
 copernicus.org/acp-6-4643-2006.pdf |
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| Zusammenfassung |
| The most direct approach for measuring the exchange of biogenic volatile
organic compounds between terrestrial ecosystems and the atmosphere is the
eddy covariance technique. It has been applied several times in the last few
years using fast response proton-transfer-reaction mass spectrometry
(PTR-MS). We present an independent validation of this technique by applying
it to measure the water vapour flux in comparison to a common reference
system comprising an infra-red gas analyser (IRGA). Water vapour was
detected in the PTR-MS at mass 37 (atomic mass units) corresponding to the
cluster ion H3O+·H2O. During a five-week field
campaign at a grassland site, we obtained a non-linear but stable
calibration function between the mass 37 signal and the reference water
vapour concentration. With a correction of the high-frequency damping loss
based on empirical ogive analysis, the eddy covariance water vapour flux
obtained with the PTR-MS showed a very good agreement with the flux of the
reference system. The application of the empirical ogive method for
high-frequency correction led to significantly better results than using a
correction based on theoretical spectral transfer functions. This finding is
attributed to adsorption effects on the tube walls that are presently not
included in the theoretical correction approach. The proposed high-frequency
correction method can also be used for other trace gases with different
adsorption characteristics. |
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